1. Field of the Invention
The present invention relates to an apparatus for adjusting a vertical stroke of a slide of a press machine.
2. Description of the Related Art
Apparatus exists which is capable of changing a vertical stroke of a slide in order to improve the productive efficiency to comply with the size and kinds of goods produced by the press machine or to provide general usability in a single press machine (Examined Published Japanese Utility Model Applications Sho 54-42305 and 55-13039, and Japanese Patent Application Hei 1-30696). In these devices, an eccentric sleeve is coupled to an eccentric portion of a crankshaft which moves the slide vertically. A connecting rod fits over the eccentric sleeve at its upper end and connects with the slide at its lower end. By turning the eccentric sleeve around the eccentric portion of the crankshaft, the angular phase between the eccentric portion of the crankshaft and the eccentric sleeve can be changed to adjust the vertical stroke of the slide when the crankshaft is rotated.
In both the Examined Published Utility Model Applications Sho 54-42305 or 55-13039, the rotation of the eccentric sleeve around the eccentric portion of the crankshaft is performed by manually turning the eccentric sleeve using a tool or by turning a bolt. In Patent Application Hei 1-30696, the eccentric sleeve is fitted axially slidably over the eccentric portion of the crankshaft. If the eccentric sleeve is slid axially, teeth are engaged and disengaged so that the eccentric sleeve is selectively coupled to and separated from the eccentric portion of the crankshaft or the connecting rod. If the eccentric sleeve is separated from the eccentric portion of the crankshaft and the crankshaft is then turned, the angular phase between the eccentric sleeve and the eccentric portion of the crankshaft is changed.
The operator is required to make a manual adjustment using a tool or the like when the vertical stroke of the slide is to be changed as in Examined Published Utility Model Applications 54-42305 and 55-13039, which suggests it takes much time and labor, so that these conventional arrangements are inefficient and cannot be automated.
In the Application Hei 1-30696, it should be ensured that the teeth of the the eccentric sleeve, eccentric portion of crankshaft and the connecting rod engage and disengage from each other each time the eccentric sleeve slides axially. In order to do so, the teeth engage smoothly when the angular phase between the eccentric sleeve and the eccentric portion of the crankshaft is changed. In order to ensure smooth engagement of the respective teeth, engagement must be adjusted to result in a predetermined positional relationship between the respective teeth. In the Patent Application Hei 1-30696, the crankshaft is supported by two bearings between which the eccentric sleeve, the eccentric portion and the connecting rod are disposed and those teeth are disposed between the bearings, so that adjustment of the teeth's engagement is difficult.
While a slide stroke of a single crankshaft is adjusted in the respective conventional devices, there are other press machines which include two parallel crankshafts and a plurality of connecting rods, and, more particularly, a press machine which includes connecting rods, one for each crankshaft (2-point press machine), and a press machine which includes connecting rods, two for each crankshaft (4-point press machine). In those presses, each slide stroke for the respective connecting rods is required to be changed by the same amount at the same time, The above conventional apparatus does not do this